This invention relates to the field of separation of air into components by non-cryogenic means. The invention provides a portable, membrane-based air system, which can be used for air separation, air dehydration, or both. The system of the present invention can be easily moved from one location to another.
The use of polymeric membranes to separate air into components has been known for a long time. An example of a membrane-based air separation system is given in U.S. Pat. No. 4,881,953, the disclosure of which is incorporated by reference herein. A polymeric membrane used for air separation is chosen to exhibit selectivity between oxygen and nitrogen. That is, the membrane tends to pass one component, designated the more “permeable” component, and to resist the passage of the non-permeable component. Such a membrane can therefore separate a stream of air into an oxygen-enriched stream, and an oxygen-depleted (nitrogen-enriched) stream.
A major advantage of a membrane system is that it avoids the expense and inconvenience of using cryogenic liquids. Moreover, a typical membrane system has only one moving part, namely the compressor used to supply compressed ambient air to the membrane unit. Thus, the membrane system has the advantages of inherently low maintenance and low energy consumption.
Although the essential features of a membrane-based air separation system comprise only a compressor and a membrane unit, a practical membrane system may include additional components, such as are illustrated in the above-cited patent. Because compression of ambient air may cause liquid water to appear in the stream, a moisture separator is typically used to remove the water, which would otherwise degrade the membrane. Similarly, a carbon adsorbent may be provided to remove residual hydrocarbons that might be present due to leakage of oil from the compressor. Additional heaters, moisture traps, and/or filters may be included, between the compressor and the membrane unit, as needed.
Membrane units of the prior art do have the disadvantage that they are not portable, and must be set up at each location where air separation is necessary. In many applications, such as in oil drilling, the locations are remote, and the air separation system may be required only for a short period of time at each location. It is expensive and inconvenient to set up and dismantle an air separation system repeatedly, for a plurality of oil drilling sites.
The present invention combines the advantages of a membrane-based air separation system, with the mobility of a truck, by providing a membrane system that is carried on a truck or other vehicle, and powered by the engine of that vehicle.
The combination of a truck with a membrane-based air separation unit is shown in U.S. Pat. No. 5,960,777, the disclosure of which is incorporated by reference herein. However, the system described in the cited patent uses a membrane system only to provide modified air to affect engine performance. That is, the patent uses a membrane system to enhance the operation of the engine of the truck. It does not, in itself, address the problem of the non-portability of air separation systems.
In addition to providing a portable air separation system, the present invention includes a portable air dehydration system, also operated by the engine of a truck. The air dehydration system may be operated either in conjunction with, or separately from, the portable air separation system described above.